This invention is related to devices and methods for treating tumors, and particularly to devices for localized heating of tumors.
Currently, tumor ablation is commonly performed by external beam ionizing radiation or implantable ionizing radiation probes. However, these systems often deliver the energy in a relatively imprecise manner, leading to injury of surrounding healthy tissue. Furthermore, these systems involve ionizing radiation that can cause DNA mutation and potential for future cancer development.
Over the past 20 years radiant thermal energy has been used to provide thermal tumor ablation. These systems often involve the use of microwave or electromagnetic wave energy. The foremost problem in hyperthermia, however, is the generation and control of heat in the tumor""s tissue. The effective temperature range of hyperthermia (42-45 degrees centigrade) is very small. At lower temperatures the affect is minimal; and at higher temperatures, normal cells are damaged. The response rate of tumor destruction is highly dependent on how much of the tumor is heated to a therapeutic level. Tumor temperatures are generally higher than the surrounding tissue during hyperthermia treatment because of the difference in tissue blood flow. The areas of most blood flow are heated less and tissues of less blood flow such as fat are heated more. Unfortunately, most tumors have a neovascularity which increases tissue blood flow and thus, makes the tumor less likely to heat relative to the surrounding fat. Accordingly, overheating of the surrounding fat remains a major problem, particularly in obese patients where the temperature rise may be seventeen times greater in fat than muscle due to the large difference in dielectric properties and specific heats.
Other problems particularly with inter-cavitary hyperthermia include temperature regulation. It is difficult to measure intratumor temperature by applying only external microwave or radio frequency energies. Temperatures have been measured on the surface of the tumor which may be very different from those in the tumor. Radio frequency energy can be deposited into the center of the body, but a large region is affected. Differential increases in blood flow in normal and tumor tissues may result in higher temperatures in the tumor than in normal organs. However, this temperature differential can not be ensured. Accordingly, large amounts of normal surrounding tissue may get injured during hyperthermia treatment.
More recently, various companies have developed a probe to be inserted directly into the tumor. This probe is capable of radiating thermal energy. However, most of the energy is limited to 2-5 millimeters surrounding the probe. Accordingly, uniform destruction of the tumor is difficult to obtain unless multiple probes are inserted into the tissue. Furthermore, the needles may often have to pass through normal vital tissue making needle-probe insertion hazardous or require an open surgery for insertion. More importantly, however, delivery of precise uniformly distributed energy to all the tumor cells is extremely difficult, if not virtually impossible, since the energy is concentrated at the center part of the temperature probe.
The present invention disclosed and claimed herein comprises, in one aspect thereof, a system for treating tumors. A processing unit is provided that is equipped with an antenna for transmitting and receiving signals, and including input control circuitry and display circuitry. One or more miniature substantially spherical heater balls are disposed proximate to the tumor. Each of the heater balls includes one or more heater elements and integrated circuitry for controlling the heater elements to radiate heat to the adjacent tumor. The integrated circuitry includes input/output data communication circuitry and signal processing circuitry for communicating with the processing unit to receive signals for the purpose of controlling the operation of the heater elements.